(a) Field of the Invention
The present invention relates to a method for controlling inter-cell interference, and more specifically, to a method for distributing and performing power control for inter-cell interference removal in a wireless communication system, and an apparatus thereof.
(b) Description of the Related Art
In multipath propagation environments, an orthogonal frequency division multiplexing access (hereinafter referred to as “OFDMA”) scheme, which has spectrum efficiency robustness and ability to combat inter-symbol interference (ISI), is considered to be an efficient technology in a future broadband wireless communication system. In an OFDMA-based wireless communication system, inter-carrier interference may be disregarded due to the orthogonality of subcarriers that remove the inter-cell interference.
However, a total bandwidth can be fully reused in all sectors due to a frequency reuse factor (FRF) used for increasing the throughput for the system. In this case, the inter-cell interference is considered to be main interfering source. Therefore, in the wireless communication system for reusing a frequency, the inter-cell interference is a factor limiting the system performance. As a result, the technology for controlling the inter-cell interference is important to improve the system performance, and in particular, can improve the system performance at a cell edge.
Reviewing a general interference controlling technology, it is assumed that a subchannel includes subcarriers that are distributed over total bandwidth and different frequency reuse coefficients are allocated to each subchannel. Therefore, a data ratio, which can be obtained by a user in a specific subchannel, is changed based on the frequency reuse factors due to the interference that averages the effect of frequency diversity. In this case, the frequency reuse factor allocation information on all the subchannels is collected and the interference control among all cells is performed based on the collected information. However, there is a problem in that the fact that the subchannels assumed in the control technology include the distributed subcarriers is invalid in a practical system.
As another interference control technology, there is a semi-distributed scheme that is configured of two levels of a resource allocation process, which is performed in a radio network controller (RNC) and a base station, respectively, with different time scales. The radio network controller determines an optimal combination of the user and the radio channel in the multi-cell environments under the assumption that there is only dominant interference and the base station performs the actual user selection based on a short term instantaneous channel gain. However, this scheme has a problem in that there is no fairness to the users.
As another technology, there is a fully distributed scheme that is different from the semi-distributed scheme. In this scheme, the transmission in cells that do not fully contribute capacity to outweigh the interference degradation caused by them to the rest of the network is “switched off”. In addition, even though there are several assumptions that lead to a simplified switch-off threshold value, the interference is not effectively removed when there area large number of user terminals.
As such, the existing technologies can maximize the overall throughput for the system but do not guarantee the performance of the cell edge users. In particular, in order to improve the overall throughput, the throughput for the cell edge users is disregarded.
In a wireless communication system providing ubiquitous cell coverage, it is very important to guarantee the throughput for the cell edge users. As interference control technologies considering the performance of the cell edge users, there are an interference randomization scheme, an interference cancellation scheme, and an interference control scheme that use soft frequency reuse, fractional frequency reuse, etc.
However, these schemes improve the performance of the cell edge users through the performance degradation of the user at the cell center and do not guarantee the transmission rate of the cell edge users.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.